Method of making leakproof sites of entry of domestic connector pipes and similar feed pipes into sewers

ABSTRACT

A method for producing leak-proof sites of entry for domestic connection pipes and other feed pipes into sewers. The method includes the steps of widening the site of entry of the feed pipe into the sewer, providing a barrier towards the interior of the sewer at the site of entry, providing a barrier within the feed pipe at a predetermined distance from the site of entry, introducing an expanding solidifying sealing mass into the space between the barriers so as to fill the space and any openings, fissures, or cracks found therein, clearing a path of flow from the feed pipe through the sealing mass and into the sewer, and optionally lining the flow path with a solidifying, insoluble, corrosion-resistant and non-ageing material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to construction, repair and modificationof waste water drainage systems, and more particularly, to a method ofmaking leak-proof sites of entry for domestic connection pipes and otherfeed pipes into waste water drainage systems.

2. Description of the Related Art

When constructing and renovating waste water drainage systems (e.g.sewers), it is very important that the sites of entry of feed pipes intoa drainage system be leak-proof because leaking sewage can contaminategroundwater. Unfortunately, it is often very difficult to construct aleak-proof site of entry. For example, poor accessibility to the site ofentry is a common problem in repairing or modifying a waste waterdrainage system. In most instances, drainage systems into which feedpipes enter, are not man-sized and generally are located below narrowstreets with high traffic density. Traditional methods of repairing adrainage system or modifying a drainage system require excavating thearea around the site of entry. The relatively high monetary costs ofsuch earthwork are often increased by expenditures caused by trafficrequirements, such as the provision of detours. Therefore, a need existsfor a method to construct, repair and modify waste water drainagesystems that avoids the costs associated with excavating the area aroundthe site of entry and more importantly, provides a leak-proof site ofentry that eliminates groundwater contamination from leaking sewage.

Various methods of making sites of entry of feed pipes into sewers havealready been suggested. However, these methods insufficiently meet theobject of providing well sealed sites of entry of the type discussedherein. For example, according to DE-A-37 00 883, in man-sized sewerswhich are provided with a lining made of bent plate elements, ahose-like, mortar-filled collar surrounding the site of entry isinserted between the sewer wall and the lining to form a leak-proof siteof entry. The insertion of such a collar is hardly feasible if the seweris not man-sized. Furthermore, it must be taken into account that themortar filling of this hose-like collar will not permit this collar tosnugly fit around all sealing sites, and thus leaks may still occur.

In EP-A1-403 773, annular or hose-shaped seals are provided between theinner pipe and the sewer wall at a site of entry of a lateral feed pipein a sewer renovated with an inner pipe to avoid the penetration ofwaste-water coming from the feed pipe into the gap present between thesewer wall and the inner pipe. The insertion of such seals is difficult,and this technique requires that the pipe forming the lateral connectionis fitted sufficiently leak-proof in the sewer wall. If such aleak-proof fit is not ensured, waste-water can leak into the surroundingsoil.

EP-A1-350 802 describes a technique which provides for the insertion ofan inner pipe into a main train of sewer pipes when renovating pipingsinto which feed ducts, e.g. from domestic connections, enter laterally,with the annular space formed between the original pipe wall and theinner pipe being filled with a mortar mass. At the sites of entry,apertures are formed starting from the interior of the inserted innerpipe by cutting through the wall of the inner pipe and the mortar layer,thereby forming a flow connection between the sites of entry and themain train of pipes. As a rule, the connection of the feed ducts withthe main train of pipes remains in its original state and will not bechanged even if moderate eccentricities occur when cutting out theapertures. Further, spraying a thin layer of artificial resin at theside faces of the transition may be considered. A thorough eliminationof possible faults in the attachment of the feed ducts to the main trainof pipes, however, is not provided for by this technique.

According to a further technique which is described in U.S. Pat. No.4,728,223, after insertion of an inner pipe into the main train ofpipes, apertures are cut into this inner pipe at those sites where thefeed ducts enter into the main train of pipes. A filling element is theninserted into the feed ducts at the site of entry. This filling elementprojects into the interior of an inner pipe introduced into the maintrain of pipes. The filling element then places filler in the annularspace between the inner pipe and the wall of the main train of pipes.However, treatment of the site of connection of the feed pipes with themain train of pipes which would repair any damage present in this regionis not provided for by the technique.

Finally, a technique for renovating old sewers by inserting new innerpipes of synthetic material is described in U.S. Pat. No. 4,245,970. Theregion of entry of sewer branch pipes into the main sewer is filled witha filler by means of a nozzle passed through an inflatable sealing ring.Subsequently, an aperture for passage as far as necessary into theinterior of the inner pipe is formed by a cutting tool. However,cavities, fissures or gaps which may be present at the site of entryoften are only insufficiently sealed by this technique.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodof producing leak-proof sites of entry into waste water drainagesystems.

Another object of the invention is to provide a method of constructing,repairing or modifying waste water drainage systems that avoids themonetary costs associated with traditional methods of constructing,repairing and modifying a site of entry.

It is another and more particular object of the invention to provide amethod suitable both for constructing and renovating sites of entry, andfor renovating feed pipes with an intact drainage system, and forcarrying out such work in connection with the renovation of a drainagesystem by the insertion of an inner pipe into the drainage system.

The invention is a method for producing a leak-proof site of entry intoa waste water drainage system in a manner that eliminates the need toexcavate the drainage system and the site of entry. In the method, theedge of the site of entry into the drainage system (e.g. a sewer) iswidened by forming a recess extending along the same edge. The site ofentry is closed towards the interior of the sewer and from inside thefeed pipe to form a space encompassing the site of entry. A solidifying,sealing mass is then introduced into the space formed at the site ofentry. After the sealing mass sets, the flow path through the feed pipeand into the sewer is cleared of excess sealing mass. Preferably, acover layer of solid or solidifying, insoluble, corrosion-resistant andnon-ageing material is applied onto the inner face of the site of entrywhich is sealed by the sealing mass. In this manner, a leak-proof andstrong connection can be made between domestic connection pipes and feedpipes entering into a waste water drainage system. Any damaged areaspresent in the region of the site of entry, such as broken out portionsof pipe, transition gaps and fissures or similar damage, as well asfaulty areas due to offsets between feed pipes and the entry aperturesin the sewer wall, can be filled or repaired and replaced by the sealingmass, and thus renovated.

The invention also eliminates some of the problems associated with theprecision required to renovate sewer connections. For example, a precisemachining of the entry-side rim of the feed pipe corresponding to thecurvature of the sewer wall prevailing at the site of entry is no longernecessary. Using the invention, it is possible to make this relativelycomplicated spacial intersection form automatically when removing thesealing mass, as is typically done in the course of clearing the flowpath through the feed pipe into the sewer.

Another embodiment of the method of the invention includes inserting aninner pipe into the existing sewer. As an option, filler can be placedin the annular space between the inner pipe and the sewer. Afterplacement of the inner pipe, and filler if desired, into the sewer, thesite of entry is widened and sealed as described above. It should benoted that the cutting and widening of the site of entry may be effectedboth from the interior of the sewer or main train of pipes as well asfrom the pipe or feed pipe.

A variant to the last-mentioned embodiment of the invention includesintroducing an inner pipe into the sewer wherein the diameter of theinner pipe is such that the inner pipe also forms a cover at the site ofentry effectively closing off the interior of the sewer. The sealingmass is then introduced at the site of entry as previously described.

The invention can also be utilized in connecting new feed pipes toexisting drainage systems. In this embodiment of the method, the feedpipe is brought up to the drainage system and a space is maintainedbetween the connecting end of the feed pipe and the inner wall of thesewer. This space is bridged by introducing the solidifying sealing massat the site of entry and removing the sealing mass present in the flowpath of the feed pipe.

The method of the invention is particularly useful if an existing feedpipe is to be provided with an inner pipe. In this embodiment, an innerpipe of smaller diameter is placed into the existing feed pipe, therebycreating an annular space. A sealing mass is then introduced into thearea of the site of entry. The sealing mass not only seals the site ofentry but also flows into the annular space defined by the feed pipe andthe inner pipe, thereby creating a stable and leak-proof connection.

Another embodiment of the method of the invention that provides improvedmechanical stability and particularly good anchoring of the sealing massutilizes a double-walled inner pipe wherein the two walls of the innerpipe are interconnected by a plurality of radially extending webs. Theouter wall of the double-walled pipe is provided with apertures in thearea around the site of entry, or is removed, and preferably is onlypartially removed, so that when the sealing mass is introduced at thesite of entry, the sealing mass is also guided between the webs and tothe inner wall of the double-walled pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a longitudinal cross-section of a connection between a feedpipe and a sewer;

FIG. 1b is a longitudinal cross-section of the connection of FIG. 1aafter placement of a sealing mass at the point of entry of the feed pipeinto the sewer;

FIG. 1c is a longitudinal cross-section of the connection of FIG. 1bafter the removal of the sealing mass from the path of flow;

FIG. 2a is a longitudinal cross-section of a connection between a feedpipe and a sewer which utilizes a double-walled inner pipe within thesewer;

FIG. 2b is a longitudinal cross-section of the connection of FIG. 2aafter removal of a sealing mass from the path of flow;

FIG. 3a is a longitudinal cross-section of an alternative connectionbetween a feed pipe and a sewer;

FIG. 3b is longitudinal cross-section of the connection of FIG. 3ashowing a recess formed at the site of entry;

FIG. 3c is a longitudinal cross-section of the connection of FIG. 3bafter placement of a sealing mass at the site of entry;

FIG. 3d is a longitudinal cross-section of the connection of FIG. 3cafter removal of the sealing mass from the path of flow;

FIG. 4a is a longitudinal cross-section of an alternative connectionbetween a feed pipe and a sewer;

FIG. 4b is a longitudinal cross-section of the connection of FIG. 4aafter placement of a sealing mass at the site of entry;

FIG. 4c is a longitudinal cross-section of the connection of FIG. 3bafter the removal of the sealing mass from the path of flow;

FIG. 5a is a longitudinal cross-section of an alternative connectionbetween a feed pipe and a sewer;

FIG. 5b is a longitudinal cross-section of the connection of FIG. 5ashowing a recess formed at the site of entry;

FIG. 5c is a longitudinal cross-section of the connection of FIG. 5bafter placement of a sealing mass at the site of entry; and

FIG. 5d is a longitudinal cross-section of the connection of FIG. 5cafter removal of the sealing mass from the path of flow.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be further explained with reference to examplesillustrated in the accompanying figures.

FIGS. 1-5 are longitudinal cross-sections showing various feed pipeconnections into drainage systems. FIGS. 1a-1c illustrate one embodimentof the invention. In FIG. 1a, a sewer 1 extends in the soil 23. A feedpipe 6 discharges into the sewer 1 in the region of the site of entry 9.As an aid to understanding the usefulness of the invention, the site ofentry 9 has been drawn to include various types of damage, such asbroken out portions 13a, transition gaps 13b and fissures 13c. To repairthe damage present at the site of entry, a sewer inner pipe 3 isintroduced into the sewer 1, and a feed inner pipe 7 is introduced intothe feed pipe 6. The edge of the site of entry of the pipe 6 is widenedby forming a recess 15a indicated by the phantom line. By forming therecess, broken out portions, gaps and fissures present at the site ofentry 9 are largely removed. The forming of recess 15a can beaccomplished using a milling robot or similar cutting device introducedvia the feed pipe 6.

Preferably, the feed inner pipe 7 is not guided all the way to theinterior of the sewer 1. A space is maintained between the connectingend of the pipe 7 and the wall of the sewer inner pipe 3. As shown inFIG. 1b, an injection device 16 comprising a feed duct 18 and aninjection nozzle 19 is introduced via the feed inner pipe 7. The innerspace of the pipe 7 is closed externally of the site of entry 9 by aradially expandable disc 17 which is in contact with the injectiondevice 16. Sewer inner pipe 3 present in sewer 1 forms a cover closingthe site of entry 9 at the inner side of the wall of the sewer 1creating a space that encompasses the site of entry and is defined bythe outer wall of sewer inner pipe 3 and the disc 17. A pressure-proof,leak-proof connection of feed pipe 6 to sewer 1 is then created byintroducing a sealing mass 12. The sealing mass 12 is introduced intothe defined space in a sufficient amount and at sufficient pressure tofill the entire defined space including the recess 15a and all fissuresand cracks located therein (e.g. 13a, 13b, 13c).

As shown in FIG. 1c, after the sealing mass 12 is solidified, a millingdevice 20 or other appropriate milling, drilling or cutting device isused to remove sealing mass corresponding to the inner diameter of thepipe 7 to clear a flow path for the feed pipe 6 into the sewer 1. Themilling, drilling or cutting device 20 is advanced at the site of entrythrough the feed inner pipe 7 into the interior of the sewer 1, and thesolidified sealing mass is removed according to the cylinder shape 15shown in broken lines.

The sewer inner pipe 3, whose wall is still completely closed at thesite of entry 9 at the time the sealing mass 12 is introduced, is partlyremoved or cut out in registration with the inner space of the feedinner pipe 7, together with the sealing mass present in the flow path ofthe pipe 6. Thus, a pressureproof, leak-proof connection 11 is formedwhich consists of the remaining solidified sealing mass 12 and extendsfrom the connecting end of the feed inner pipe 7 into the interior ofthe sewer 1. In this manner, an automatic adaptation of the edge shapeof the feed duct formed with the feed inner pipe 7 to thecircumferential shape of the sewer 1 is achieved, thus eliminating acomplex processing of the connecting end of the feed inner pipe 7.

In the embodiment of the method according to FIGS. 1a-1c, the externaldiameter of the feed inner pipe 7 is only slightly smaller than theinternal diameter of the feed pipe 6, and the annular gap presentbetween these feed pipes 6 and 7 is sealed by the sealing mass 12entering into this annular gap. The sealing mass 12 can also fill gapspresent between the wall of the sewer 1 and the sewer inner pipe 3inserted into the sewer 1.

The penetration of the sealing mass into the branches of the cavitiespresent at the site of entry 9 may be controlled by selection of theinjection pressure as well as by selection of the composition of thesealing mass. Expanding sealing masses are advantageous. A sealing massin the form of a two-component synthetic resin foam that hardens in thepresence of moisture, that displaces water and that quickly solidifiesis particularly preferred. A polyurethane foam that swells and thus"crawls" is particularly suitable. Such a foam will even enter into gapsof 0.1 mm width and harden to a material of considerable staticstrength. It is advantageous to choose a type of foam material which isnon-ageing, waterproof, and resistant to domestic chemicals as well asto chemical aggression by substances present in the soil. A swellingpolyurethane foam strongly contacts surfaces delimiting the foam bodyand thus prevents the entry of water at the areas of contact whilesimultaneously providing a certain degree of elasticity so that minormovements can be accommodated without substantially affecting theleak-proof contact of the foam. Such properties can also be attainedwith other suitable materials.

The closure of the interior of the feed pipe 6, can be accomplished invarious ways. An inflatable balloon or a similar closing device can beprovided on the injection device 16 instead of a radially expandabledisc 17. An inflatable balloon may offer advantages, because it may beguided easily through narrow passages.

FIGS. 2a and 2b illustrate another embodiment of the method. In thisembodiment, recess 15a is again formed at the site of entry 9. Adouble-walled sewer inner pipe 3a is introduced into the sewer 1 to berenovated. The two walls of pipe 3a are interconnected by a plurality ofradially extending webs so that the wall of this pipe 3a, seen as awhole, is formed of a large number of mutually closed compartments. Apipe having such a structure has a good mechanical stability withrelatively low weight and offers increased safety against undesired wallperforations. In the region of the site of entry 9, the outer wall ofthis double-walled pipe 3a is provided with apertures 3b or is partlyremoved. The sealing mass introduced in the course of the process intothe cavities present at the site of entry 9 can enter into thecompartments of pipe 3a opened by the apertures 3b and thus can anchoritself well in pipe 3a as illustrated in FIG. 2b. The slit-shapedapertures 3b may be made before introducing the sewer inner pipe 3a intothe sewer 1, or they may be made when the inner pipe 3a is already inplace by means of a correspondingly controlled milling robot introducedvia the feed pipe 6. The cavities at the site of entry 9 are filled aspreviously described. When the sealing mass has solidified, the flowpath can be cleared using a milling device or other clearing device aspreviously described. Thus, the leak-proof site of entry 10 of the feedpipe 6 into the sewer 1 and its sewer inner pipe 3a is formed, asillustrated in FIG. 2b.

In an alternative embodiment of the method illustrated in FIGS. 2a and2b, a double walled pipe may be used for the feed inner pipe 7. Sealingalong such a pipe 7 would be in the same manner as that shown for sewerinner pipe 3a in FIG. 2b. Such a double-walled design of a feed innerpipe 7 offers the advantage of a very stable anchoring of the connectingend of the feed pipe to the sealing mass.

FIGS. 3a-3d illustrate yet another embodiment of the method. At the siteof entry 9, the edge of the entry is provided with a recess 15a (FIG.3b). Again, damaged parts which have an unfavorable shape for thepenetration of the sealing mass, (e.g. narrow slits and the cavitiesthere behind, or lateral offsets 13d of the feed pipe 6) can be removedby this recess. The recess 15a is again made by a milling robotintroduced via the feed pipe 6.

The embodiment illustrated in FIGS. 3a-3d show that even with a sewerinner pipe 3 of markedly smaller diameter as compared to the diameter ofthe sewer 1, this inner pipe 3 can form a cover closing the site ofentry 9 at the inner side of the sewer wall, without requiring fillingof the annular space 4 there between with a filler. Such an embodimentwill be suitable if both the sewer 1 and the sewer inner pipe 3 havesufficient static stability or strength. When the sealing mass 12 isintroduced by means of the injection device 16 inserted via the feedpipe 6 (FIG. 3c), the cavities located in the region of the site ofentry 9, the recess 15a and the annular space 4 in the region of thesite of entry 9 are filled with the sealing mass. The distance passed bythe sealing mass 12 into the annular space 4 can be adjusted byappropriate adjustment of the flow or solidifying parameters of thesealing mass 12 or by adjusting the injection pressure. The sealing mass12 flowing into the annular space 4 at the site of entry 9 provides asupport for the sewer inner pipe 3 in the sewer 1.

Subsequently, as shown in FIG. 3d, the flow path from the feed pipe 6into the sewer 1 and the sewer inner pipe 3, can be cleared by anappropriate clearing device 20 forming a cylindrical cut-out 15. Thus, apressure-proof, leak-proof connection of the feed pipe 6 with the sewerinner pipe 3 of the sewer 1 is formed, as schematically illustrated inFIG. 3d. It should be pointed out that in this finished state, the entryaperture formed in the sewer inner pipe 3 registers with the feed pipe6. The originally present lateral offset is eliminated. If desired, afeed inner pipe 7 may also be used as shown in FIG. 1a.

The process may be modified in that the recess 15a can be formed beforea sewer inner pipe 3 is introduced into sewer 1. Likewise, if desired,the annular space 4 between the wall of the sewer 1 and the sewer innerpipe 3 may be filled with a filler before the sealing mass is introducedinto the cavities present at the site of entry 9.

Yet another embodiment of the method is illustrated in FIGS. 4a-4c.These figures relate to the renovation of a sewer 1 that has beenpreviously renovated by introduction of a sewer inner pipe 3. At theentry aperture 10 to which the feed pipe 6 is joined, the sewer innerpipe 3 is provided with an entry aperture 14 as shown in FIG. 4a.Damaged portions, (broken out portions 13a, transition gaps 13b andfissures 13c) may be present in the region of the site of entry 9, whichrequire repair. As with the previous embodiments, a recess 15a is formedby widening the site of entry 9. This recess extends to the sewer innerpipe 3.

Furthermore, in this embodiment the feed pipe 6 is to be renovated byinsertion of a feed inner pipe 7. The feed inner pipe 7 has asubstantially smaller diameter than the feed pipe 6 so that thereremains an annular space 8 between these two pipes. As shown in FIG. 4b,the aperture 14 is closed towards the sewer interior by a cover 21. Thefeed inner pipe 7 is closed by a closing device 17 provided on aninjection device 16 supplied via the feed inner pipe 7. Subsequently,sealing mass 12 is introduced by the injection device 16 into thecavities located in the region of the site of entry 9. As shown in FIG.4c, when the sealing mass has solidified, the cover 21 and the injectiondevice 16 including the closing device 17 are removed, and a millingdevice 20 is introduced via the feed inner pipe 7 to clear a path offlow from feed inner pipe 7 through the solidified mass and into sewerinner pipe 3. This path of flow is illustrated by broken lines 15 inFIG. 4c.

In yet another embodiment of the method, some stages of which areillustrated in FIGS. 5a-5d, a defective site of entry of a feed pipe 6into a sewer 1 previously renovated by installation of a sewer innerpipe 3 is repaired so that a leak-proof entry of the feed pipe 6 intosewer 1 or the sewer inner pipe 3 is formed. The sewer inner pipe 3provided for lining sewer 1 in this instance has a markedly smallerexternal diameter than the diameter of the inner wall of the sewer 1.The annular space 4 between the outer side of the sewer inner pipe 3 andthe inner side of the sewer 1 is filled with a filler 5 (i.e. "closed bya dam", as this is called in the art).

In this embodiment, the edge of the entry aperture 10 provided in thesewer wall is widened by forming a recess 15a, as shown in FIG. 5b,whereby part of the damaged portions, (e.g. broken out portions 13a andfissures 13c) are removed. Simultaneously, the aperture 14 in the innerpipe is widened and the filler 5 present there is removed. Subsequently,the cavity located in the region of the site of entry 9 is coveredtowards the interior of the inner pipe 3 by a covering device 21 (FIG.5a), and the feed pipe 6 is closed towards its feed side by a closingdevice 17. The closed cavity is then filled with a sealing mass 12 by aninjection device 16 comprising a feed duct 18 and an injection nozzle19. The sealing mass 12 fills the recess 15a and any damaged portionsthat might have remained. The edge of the filler 5 facing the site ofentry and located in the annular space 4 between the sewer wall and thesewer inner pipe 3, is covered by the sealing mass 12, and thus isprotected from a corrosive attack by waste water. When the sealing mass12 has solidified, the cover device 21, the injection device 16 and theclosing device 17 are removed. A cut-out 15 indicated by the brokenlines in FIG. 5d is then formed by a milling device 20 or other suitablecutting device that removes the sealing mass 12 located in the flow pathfrom the feed pipe 6 to the sewer inner pipe 3. In this manner aleak-proof entry is created from the feed pipe 6 into the sewer innerpipe 3.

If particularly good corrosion resistance and non-ageing properties aredesired for the pipe wall surfaces remaining at the site of entry andlying in the flow path of the waste water and if an appropriate materialfor the sealing mass cannot be used, (e.g., because the sealing mass hasto meet other requirements, such as a very good deformability) it ispossible, as is illustrated in FIG. 5d, to apply a cover layer 22 ofsolid or solidifying, insoluble, corrosion-resistant and non-ageingmaterial to the inner face of the entry. This applies equally as well toall of the embodiments of the method described herein.

I claim:
 1. A method for producing a leak-proof site of entry for a feed pipe into a sewer, the method comprising the steps of:(a) widening the site of entry by forming a recess in the vicinity of the site of entry; (b) providing a barrier towards the interior of the sewer at the site of entry; (c) providing a barrier within the feed pipe at a predetermined distance from the site of entry; (d) introducing an expanding solidifying sealing mass between the barrier towards the interior of the sewer and the barrier within the feed pipe; and (e) clearing a path of flow through the feed pipe into the sewer.
 2. A method according to claim 1 wherein the step (b) of providing a barrier towards the interior of the sewer at the site of entry comprises the step of inserting a sewer inner pipe into the sewer.
 3. A method according to claim 2 wherein the step (b) of providing a barrier towards the interior of the sewer at the site of entry comprises the further step of placing a filler into the annular space between the sewer inner pipe and the sewer wall.
 4. A method according to claim 1 comprising the further steps of:(a1) inserting a feed inner pipe into the feed pipe; and (a2) maintaining a space between the end of the feed inner pipe adjacent the site of entry and the inner wall of the sewer.
 5. A method according to claim 4 wherein the step (b) of providing a barrier towards the interior of the sewer at the site of entry comprises the step of inserting a sewer inner pipe into the sewer.
 6. A method according to claim 5 wherein the step (b) of providing a barrier towards the interior of the sewer at the site of entry comprises the further step of placing a filler into the annular space between the sewer inner pipe and the sewer wall.
 7. A method according to claim 1 wherein the step (b) of providing a barrier towards the interior of the sewer at the site of entry comprises inserting a double-walled sewer inner pipe having an inner wall and an outer wall defining an annular space therebetween and interconnected by a plurality of radially extending webs, the outer wall being provided with apertures in the vicinity of the site of entry so that the expanding solidifying sealing mass will be introduced into the annular space defined by the inner wall and the outer wall.
 8. A method according to claim 1 comprising the further step (f) of lining the path of flow through the feed pipe into the sewer with a solidifying, insoluble, corrosion-resistant and non-ageing material.
 9. A method for producing a leak-proof site of entry for a feed pipe into a sewer, the method comprising the steps of:(a) placing the feed pipe in close proximity to the sewer; (b) maintaining a space between the end of the feed pipe adjacent the site of entry and the inner wall of the sewer; (c) widening the site of entry by forming a recess in the vicinity of the site of entry; (d) providing a barrier towards the interior of the sewer at the site of entry; (e) providing a barrier within the feed pipe at a predetermined distance from the site of entry; (f) introducing an expanding solidifying sealing mass between the barrier towards the interior of the sewer and the barrier within the feed pipe; and (g) clearing a path of flow through the feed pipe into the sewer.
 10. A method according to claim 9 wherein the step (d), of providing a barrier towards the interior of the sewer at the site of entry comprises the step of inserting a sewer inner pipe into the sewer.
 11. A method according to claim 10 wherein the step (d) of providing a barrier towards the interior of the sewer at the site of entry comprises the further step of placing a filler into the annular space between the sewer inner pipe and the sewer wall.
 12. A method according to claim 9 comprising the further steps:(c1) inserting a feed inner pipe into the feed pipe; and (c2) maintaining a space between the end of the feed inner pipe adjacent the site of entry and the inner wall of the sewer.
 13. A method according to claim 12 wherein the step (d) of providing a barrier towards the interior of the sewer at the site of entry comprises the step of inserting a sewer inner pipe into the sewer.
 14. A method according to claim 13 wherein the step (d) of providing a barrier towards the interior of the sewer at the site of entry comprises the further step of placing a filler into the annular space between the sewer inner pipe and the sewer wall.
 15. A method according to claim 9 wherein the step (d) of providing a barrier towards the interior of the sewer at the site of entry comprises inserting a double-walled sewer inner pipe having an inner wall and an outer wall defining an annular space therebetween and interconnected by a plurality of radially extending webs, the outer wall being provided with apertures in the vicinity of the site of entry so that the expanding solidifying sealing mass will be introduced into the annular space defined by the inner wall and the outer wall.
 16. A method according to claim 9 comprising the further step (h) of lining the path of flow through the feed pipe into the sewer with a solidifying, insoluble, corrosion-resistant and non-ageing material. 